This invention relates to an adsorption element for adsorption of gases and vapors from the gas atmosphere in the gas stream of the intake tract of an internal combustion engine, and to a method for adsorbing gases such as hydrocarbon vapors in return flows from an internal combustion engine.
Adsorption elements are used for air intake systems of internal combustion engines, for example. The adsorption elements here have the function of adsorbing hydrocarbons which threaten to escape from the intake system after the engine is shut down. When the engine is subsequently operated again, the hydrocarbons are again desorbed from the adsorption element into the air intake stream and are then burned in the engine which restores the capacity of the adsorption element.
For example, U.S. Pat. No. 5,914,294 (=CA 2,367,031) discloses a monolith which adsorbs chemical constituents from a gas stream. This is achieved by bringing the gas stream into direct contact with an activated carbon layer in its flow through the monolith. One disadvantage of this type of extruded or pressed monolith adsorption element is that they are preferably manufactured from powdered activated carbon and a binder and therefore have a brittleness which leads to the risk of individual fragments flaking off. In addition, the adsorption capacity is reduced by the fact that the binder partially blocks the pore system of the adsorption medium. When using monoliths as the adsorption element, additional filter elements are therefore necessary to retain particles of the adsorption element that have become detached and prevent them from entering the gas stream. The incorporation of additional filter inserts means an increased complexity and increases the flow resistance in the intake tract. Thus, despite the efforts of the prior art, there has remained a need for improved devices and methods for adsorbing hydrocarbon vapors from return flows in the intake tract of an internal combustion engine.